Note: Descriptions are shown in the official language in which they were submitted.
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FIRE SUPPRESSION SYSTEM
Field of the Invention
The present invention relates to a fire
suppression system and method for extinguishing fires by
dispensing a fire extinguishing composition onto the fire
followed by the application of water. The system can
utilize a particular extinguishing composition which
comprises a unique mixture of at least two salts wherein
the mixture exhibits a single minimum melting point.
Backaround of the Invention
In the fire extinguishing art, fires are divided
into four general classes; namely, Class A, Class B, Class
C and Class D.
Class A fires are those involving ordinary
combustible material such as paper, wood, etc. and can be
extinguished by quenching and cooling with large
quantities of water or solutions containing a large
percentage of water.
Class B fires are those involving shortening,
oils, greases, flammable liquids, etc. In this type of
fire, the use of water is generally ineffective, because
the contact of water with the hot oil causes a great
amount of splattering without extinguishing the flames and
the hot burning oil or grease may spread the fire. This
type of fire is the most difficult to extinguish because
of the low auto-ignition points of shortening, oils and
greases which are in the range of about 360 C to 380 C.
Further, the presence of flammable materials in large
quantities makes it extremely important to extinguish the
fire as rapidly as possible and also bring the temperature
down to prevent any reflash which occurs at a lower
temperature of about 337 C.
Class C fires involve electrical equipment.
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Thus, the electrical conducting property of the
extinguishing material is an important consideration. For
this reason, it has been found that dry fire extinguishing
agents are generally more useful. It has also been found
that the fire extinguishing agents useful for Class B
fires are generally also useful for Class C fires.
Class D fires involve combustible metals and are
extinguished with special dry powders.
Many different fire extinguishing compositions
and fire extinguishing systems using such compositions
have been developed and are available on the market.
However, re-flash or auto- ignition of the hot shortening,
oils or greases in Class B fires remains a serious
problem. This is true, particularly, when such fires
involve large commercial establishments, such as
restaurants, cafeterias, mess halls, etc. The potential
danger of such fires in these types of establishments is
widely recognized.
Prior art systems for extinguishing fires in
cooking equipment in a kitchen have utilized a water
spray. When such systems are employed, the time to
extinguish fat, oil, shortening or grease fires may take
up to six minutes. The water spray can cause violent
flaming. In such systems, the fat, oil, shortening or
grease fire is eventually extinguished because of the
cooling action of the applied water on the hot oil or
grease. A system which utilizes water spray fire
protection for hoods over cooking units is shown in U.S.
Pat. No. 4,356,870. Another system which automatically
releases a high volume flow of extinguishant over critical
areas of a fat or grease fire is disclosed in U.S. Pat.
No. 3,584,688.
Various state-of-the-art restaurant fire
protection systems use proprietary wet chemical agents to
suppress hostile fires in hoods, ducts and cooking
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appliances. These wet agents are typically aqueous
solutions of organic salts specifically formulated to
suppress fuel-in-depth grease fires in two distinct
phases. During the first phase, the agent is sprayed
directly onto the grease fire for rapid extinguishment
(approximately 5 seconds) of the flames by chemical
reaction. In the second phase, the wet agent continues to
be discharged onto the hazard to both cool and combine
with the hot grease to generate a protective foam blanket
on top of the hot grease. The foam blanket secures the
hot grease from reflashing by excluding air until the
grease either cools down below its reflash temperature or
the foam blanket breaks down from the heat of the hot
grease below, or both. The water content in the wet agent
is an effective cooling agent (a positive feature) but is
offset by the insulating effect of the foam blanket which
retards the heat release of the hot grease (a negative
feature). When water alone is sprayed onto a grease fire,
it has proven to be a poor extinguishing agent but an
effective cooling agent, provided it is discharged for an
extended period of time (for an average of about 6-9
minutes). In fact, water alone will not extinguish the
flames until the hot grease is cooled below its reflash
temperature.
It is an object of the present invention to
provide a fire suppression system which provides rapid
flame knockdown by the application of a wet chemical and
which also provides cooling and securement of the hot
greases, oils, shortening, fat or flammable liquid (fuels)
by further application of an unlimited amount of water.
It is a still further object of the present
invention to provide a fire suppression system which gives
better coverage over a grease or oil fire and which is
easy to install in existing kitchen equipment.
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Summary of the Invention
The present invention relates to a fire
suppression system and method in which an extinguishing
agent is automatically discharged from a limited source of
supply of the wet chemical extinguishing agent for rapid
extinguishment of the fire, followed by water application
to the locus of the fire from an unlimited source of
supply of water. The subsequent automatic application of
water provides rapid cooling of the hot burning material
below its reflash temperature. The protective foam
blanket normally generated by an extinguishing agent alone
can be negated by water spray dilution in order to
maximize the superior cooling effects of the water against
the hot burning material such as grease or fat. However,
the present hybrid system exploits the best fire
suppression properties of both agents against fires i.e.
the wet chemical extinguishing agent provides rapid flame
extinguishment and water provides rapid cooling following
extinguishment. The present hybrid system is
significantly more robust (fire test variables are less
critical to its fire suppression performance) than current
water or wet chemical agent systems.
In the dry pipe embodiment of the present
system, an extinguishing agent in liquid form is
automatically delivered to a fire by a fire suppression
system. The fire suppression system comprises a means for
automatic fire detection, a means for automatic actuation
of the suppression system, a storage vessel for an
extinguishing agent, distribution piping for the
extinguishing agent and for water, and nozzles for
spraying the wet chemical extinguishing agent and
subsequently water onto the fire. The operation of the
system is such that, at the completion of the discharge of
the extinguishing agent, an automatic switching means
provides for the subsequent application of water
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automatically through the same distribution piping and
spray nozzles of the system as are employed to apply the
extinguishing agent onto the fire.
The automatic switching means to switch from the
flow of extinguishing agent to a flow of water is
accomplished by an automatic valve. The automatic
switching valve is actuated with either gas or hydraulic
pressure, depending on which of three optional valves is
used with the dry pipe system, as described in the
following section describing the details of the present
invention by reference to the figures.
In a wet pipe embodiment of the invention, a
liquid extinguishing agent is contained within the
distribution piping and is delivered to the fire by a
system comprising a means for fire detection, a means for
automatic actuation, distribution piping for the
extinguishing agent and water, and spray nozzles for
dispensing the extinguishing agent and water onto the
fire. At the completion of the discharge of the liquid
extinguishing agent the subsequent application of water
occurs automatically by means of an automatic check valve
through the same distribution piping and spray nozzles.
The extinguishing agent can also be stored in
solid rather than liquid form within a primary storage
means and can be dissolved by the flow of water into the
primary storage means. The water flow is automatically
actuated by a means for fire detection and a means for
automatic actuation. The flow of the extinguishing agent
dissolved in water occurs through distribution piping and
spray nozzles, with the flow of water continuing after the
dissolved extinguishing agent solution is exhausted.
The extinguishing agent can also be in solid
form within multiple storage means located directly prior
to each spray nozzle and can be dissolved by the flow of
water. The flow of water is automatically actuated by a
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means for fire detection and a means for automatic
actuation. The flow of the extinguishing agent dissolved
in water occurs through the spray nozzles, with the flow
of water continuing after the dissolved salt solution is
exhausted. -
Brief Description of the Drawinas
Fig 1. is a schematic for the dry pipe
embodiment of a fire extinguishing system of the present
invention.
Fig. 2 is a schematic for the wet pipe
embodiment of a fire extinguishing system of the present
invention.
Figs. 3a, 3b and 3c are details for one valve
option for a dry pipe fire extinguishing system of the
invention.
Fig. 4a and-4b are details of a second valve
option of a dry pipe fire extinguishing system.
Fig. 5 is a detail of a third valve option of a
dry pipe extinguishing system.
Fig. 6 is a detail of a nozzle useful in the
present system.
Detailed Description of the Invention
One dry pipe embodiment of the present system is
shown in Fig. 1. A tank 3 holding a solution of the fire
extinguishing composition 1 is connected through pipes 7
to appliance nozzles 6, plenum nozzles 8 and duct nozzles
9. A valve assembly 4 (detail shown in Figs. 4 and 4b)
mounted on the tank 3 controls the sequential release of
the solution of the fire extinguishing composition
followed by water. When a fire is detected by a detection
means 10, a seal in a gas cartridge 2 release is punctured
and gas at high pressure is released from the gas
cartridge 2. The high pressure gas simultaneously presses
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a spring loaded piston against the water inlet valve (not
shown) to prevent water from being discharged and forces
the solution in the tank to be discharged through the
nozzles 6, 8 and 9. When the gas pressure is reduced to a
particular pressure, such as for example 45 psi, the
spring loaded piston of the valve assembly moves to an
open position to permit water flow down to the tank 3 and
out to the nozzles.
The embodiment shown in Fig. 2 is a wet pipe
system. Before system actuation, the storage tank 20 and
the distribution piping 21 are filled with wet agent. The
tank 20 and distribution piping 21 are under pressure from
compressed gas in the top of the agent tank. Discharge
nozzle valves 22, 23, 24 are closed. When one or more
heat-actuated nozzle valves 22, 23, 24 opens in response
to heat from hostile fire(s) wet agent is automatically
expelled from the agent tank 20 and distribution piping 21
through the open nozzles 27, 28, 29 by the compressed gas
in the tank 20. When the compressed gas pressure drops
below in the water pressure at the water inlet check valve
26, water will automatically flow through the distribution
piping 21 and the same open nozzles 27, 28, 29 until the
water supply is manually shut off. Only those nozzles 27,
28, 29 which open in response to heat from hostile fires
will automatically discharge agent and water onto the
burning hazards.
Figures 3a, 3b and 3c show cross-sections of one
automatic valve option of a dry pipe system. The storage
tank 31 is filled with wet chemical agent 32 and is under
atmospheric pressure. A valve 33 has a gas inlet port 34
which is connected to a gas pressure regulator (not shown)
on the Ansul Automan release assembly (not shown). The
gas regulator is connected to an expellant gas cartridge
which contains nitrogen or carbon dioxide expellant gas
under high pressure. The valve water inlet 35 is
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connected to a municipal water supply or restaurant wet
sprinkler system and is under static water pressure. The
double piston assembly 36 is locked in the closed position
by the spring-loaded reset pin 37 so that static water
pressure will not move the double piston assembly 36. The
valve discharge outlet 38 is piped to multiple discharge
nozzles (not shown), each aimed at a potential fire
hazard.
When a hostile fire is detected, the spring-
loaded release assembly 39 (not shown) automatically
actuates to puncture the seal of the expellant gas
cartridge (not shown), thereby releasing expellant gas
under high pressure through the pressure regulator (not
shown), where the pressure is reduced to a lower operating
pressure, and thence to the valve 33. The expellant gas
performs two functions in the tank assembly 31. First, it
thrusts the double piston assembly 36 toward the water
inlet port 35 to release the spring-loaded reset pin 37,
which retracts into a recess in the valve body as shown in
Fig. 3b. Second, the expellant gas is ported through the
valve 33 to the top of the tank where it pressurizes the
wet agent 32 to force it down the tank, up the pick-up
tube 41, through the valve discharge outlet 38 and out the
discharge nozzles (not shown). During wet agent
discharge, gas pressure on the piston 42 and liquid
pressure from the wet agent on the other piston 43 hold
the piston assembly 36 in the unlocked position against
the static water pressure.
When the wet agent has been expelled from the
tank and the gas pressure decays to a critical level, the
net force on the double piston assembly will reverse
(force to open from water pressure will be greater than
the force to continue closing under decaying gas pressure)
and the static water pressure will thrust the piston
assembly 36 towards the gas inlet 34 thereby opening the
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water inlet port 35 to the discharge outlet port, allowing
water to flow out the same discharge piping to the
discharge nozzles. The water will flow until it is
manually shut off upstream of the valve. The check ball
44 prevents water from entering the tank.
The present valve is mechanically activated
using cartridge pressure to pneumatically actuate the
valve and initiate the flow of the extinguishing agent.
In the event of a fire the actuation cartridge
pressure is released to port 34. The pressure piston
releasing the locking/reset pin number 37. This pin is
spring-loaded to pull out away from the piston when the
catch is released. Pressure ported through inlet 34 is
also directly connected to the head space of the tank
where the agent is being pushed out by the gas from the
cartridge. When the tank pressure depletes after
expelling the wet chemical agent the holding force acting
on the piston area decreases allowing the water pressure
to shuttle the valve to a water open position. Water then
flows through the distribution piping and is applied to
the extinguished hazard cooling the grease or cooking
surface and preventing reflash from occurring.
Figures 4a and 4b show another automatic valve
option of a dry pipe fire protection system. Tank 50 is
filled with a wet chemical agent 51 under atmospheric
pressure. The water inlet port 52 of the valve assembly
53 is piped to a source of water supply. The valve 53 is
closed and is under static water pressure. The connected
water line (not shown) includes a check valve (not shown)
to prevent backflow when the system is initially actuated.
The high pressure gas inlet port 54 of the valve 53 is
piped to the high pressure side of the gas pressure
regulator (not shown) on the spring-loaded release
assembly (not shown) and is under atmospheric pressure
until the fire protection system is actuated. The high
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pressure line (not shown ) includes a check valve (not
shown) to trap high pressure gas in the line when the
system is actuated. As an optional feature, the high
pressure gas line may include a bleed orifice so that the
high pressure gas is slowly released to allow water
pressure to automatically close the valve after the water
has discharged for a minimum duration, to minimize
flooding. The low pressure gas inlet port 55 on the pick-
up tube assembly is piped to the low pressure side of same
gas pressure regulator and is also under atmospheric
pressure until the system is actuated. The gas pressure
regulator (not shown ) is piped to a gas cartridge (not
shown) a small pressure vessel, which contains a fixed
volume of nitrogen or carbon dioxide expellant gas under
high pressure. The tank discharge outlet 56 on the pick-
up tube assembly 57 is piped to multiple discharge nozzles
(not shown), each aimed at a potential fire hazard.
When a hostile fire is detected by the fire
protection system, the spring-loaded release assembly (not
shown) automatically actuates to puncture the seal of the
expellant gas cartridge, thereby releasing gas under high
pressure to both the high pressure gas inlet of the valve
54 and the pressure regulator, where the high gas pressure
is reduced to a lower operating pressure. The high
pressure gas opens the valve 53 to the water supply by
thrusting the piston 59 and stem assembly 60 towards the
water inlet 52 against the force of the spring 61 and the
static water pressure. Once the stem assembly 59 is
unseated, the trapped high pressure gas will hold it open
until the gas pressure is manually released after the fire
event when the system is recharged and reset. The low
pressure gas from the regulator enters the top of tank to
expel the wet agent 51 from the tank 50 through the tank
discharge outlet 56, discharge piping (not shown ) and
discharge nozzles (not shown). Once the low pressure gas
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is flowing, the regulator will feed the low pressure gas
into the tank at a constant pressure until the decaying
pressure of the gas in the fixed-volume cartridge falls
below the preset outlet pressure of the regulator, at
which time the gas pressure from the regulator will also
decay with time.
Although the valve was opened initially by the
high gas pressure, water will not flow into the tank 50
until the water pressure from the water supply overcomes
the decaying gas pressure of the low pressure gas in the
top of the tank 50, at which time water will automatically
commence flowing through the tank 50, discharge piping and
the discharge nozzles. Water will continue to flow until
it is manually shutoff upstream from the valve after the
fire event is concluded.
Figure 5 shows a third automatic valve option of
the dry pipe system. - The automatic remote valve 70 can be
located in the agent distribution piping (not shown) of
the present fire protection system between the wet agent
storage tank (not shown) and the discharge nozzles (not
shown). The agent inlet port 71 on top of the valve is
piped to the discharge connection on the wet agent storage
tank and is under atmospheric pressure until the system is
discharged. The discharge outlet 72 on the valve is piped
to multiple discharge nozzles (not shown), each aimed at a
potential fire hazard. The water inlet port 76 on the
bottom of the valve is piped to a water supply source and
is under static water pressure. The piston 74 includes
two circumferential 0-rings (not shown) to seal against
hydraulic pressure from either side. The piston 74 is
locked in the closed position by the spring-loaded reset
pin assembly 75 to resist the static water pressure.
Because the reset pin 75 is hooked on the piston, it
cannot retract (move to the right) under spring force
until the piston is thrust downward during the operating
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cycle.
When a hostile fire is detected by the system,
the spring-loaded release assembly (not shown)
automatically actuates to puncture the seal of the
expellant gas cartridge (not shown), thereby releasing-
expellant gas (nitrogen, carbon dioxide, or air) under
high pressure through the pressure regulator (not shown),
where the pressure is reduced to a lower operating
pressure. From the regulator, the gas is routed to the
inside of the agent storage tank (not shown) where it
forces the wet agent out of the tank, through the
normally-open ports in the automatic valve 70 and out the
discharge nozzles (not shown). The hydraulic pressure of
the wet agent flowing through the automatic valve 70 will
thrust the piston 74 down against water pressure to
unlatch the reset pin 75 which will then retract under its
spring force into the wall of the valve body. While the
wet agent is flowing through the valve 70 under maximum
regulated gas pressure, the piston 74 will remain in the
closed position because the hydraulic pressure of the wet
agent against the larger diameter of the piston 74
overcomes the water pressure against the smaller diameter
of the piston.
When the wet agent has been expelled from the
tank and the gas pressure from the cartridge decays to a
critical level, the net force on the piston will reverse
(force to open from water pressure will be greater than
the force to continue closing the piston under decaying
wet agent pressure) and the piston will be thrust up to
close the agent inlet port 71 and open the water inlet
port 76 to the discharge outlet, allowing water to flow to
the discharge nozzles until it is manually shut off.
A particular system nozzle which can be used in
the present invention is shown in Figure 6.
The nozzle 80 has a swivel joint 81 so that it
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rotate up to 30 degrees in any direction from the
centerline of the body.
The nozzle 80 also includes a vane 83 which
twists or spins the fluid being discharged out of the tip
82 to stabilize the exiting spray cone. The internal bore
of the nozzle tip is machined to a configuration which
controls both the critical flow and spray angle of the
discharge. In the case of the new appliance nozzle, the
nominal flow rate will be 1.7 gallons of water per minute
(6.4 liters/min) at 80 psi nozzle pressure. Spray angle
(included angle of the cone of water being discharged)
will be a nominal 60 degrees.
The flow rates and spray angles for the nozzles
which protect ventilation hoods and ducts over the
appliances are established based on the necessary
environmental conditions of the nozzle location and based
on the known need of extinguishing agent and water at the
nozzle locus. The appliance nozzle has a built-in swivel
joint while the hood and duct nozzles do not need to
swivel.
The present invention relates to a fire
protection system which automatically actuates the
sequential discharge of a fire extinguishing composition
followed by water. The fire protection system includes
novel valve assemblies. The valve assembly may be
installed on the top of a tank holding the fire
extinguishing composition or the valve assembly may be
remote from the tank. Preferred valve assemblies are
described herein above.
Fire extinguishing systems for use in a
commercial kitchen are usually installed as a part of the
exhaust hood over the cooking range.
The instant fire extinguishing system can be
employed using various known extinguishing agents.
Different types of nozzles with different flow rate
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controls and different spray angles are required for the
different cooking appliances such as deep fryers, griddles
and ranges.
A preferred fire extinguishing composition which
is disclosed in concurrently filed copending patent
application Serial No. entitled A COMBINATION OF
A NOVEL FIRE EXTINGUISHING COMPOSITION EMPLOYING A
EUTECTIC SALT MIXTURE AND WATER AND A METHOD OF USING SAME
TO EXTINGUISH FIRES and this preferred composition is
especially advantageous in the operation of the present
fire suppression system. The copending application is
expressly incorporated herein by reference.
The preferred novel fire extinguishing
composition comprising a unique mixture of at least two
salts I and II, wherein I is selected from the group
consisting of a carbonate or bicarbonate of sodium or
potassium and II is selected from the group consisting a
chloride, sulfate, or tartrate salt of sodium or
potassium, and the mixture I and II exhibits a single
minimum melting temperature range by DSC. The mixture is
particularly effective when applied as a combination with
additional water. The characteristic of this unique
mixture is analogous to that of a eutectic wherein a
mixture of two or more metals or salts exhibit a minimum
melting point. I is a salt having the following
characteristics: it dissociates to form carbon dioxide
when heated, and it is soluble at a range of about 25 g to
150 g/100m1 of water. II is a salt or a mixture which
when mixed at a particular ratio with I will provide a
single minimum melting temperature range. It was found
that by adding a small amount from 10 mole% to 20 mole% of
II to I, the mixture exhibits a single minimum melting
temperature range, lower than that of I alone or II alone.
Also, at this temperature, the heat capacity of the
mixture, its ability to absorb heat, is at a maximum, a
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value that is in excess of the heat capacity of the
individual components. The single minimum melting
temperature range is determinable by the use of
differential scanning calorimetry (DSC).
It is found that when the unique mixture is
applied as a fire extinguishing agent followed by water,
the combination is extremely effective for extinguishing
Class B fires involving oils or greases and will prevent
re-flash/auto-ignition. The mixture may be sprayed onto a
fire as a concentrated aqueous solution of about 15!k-30%
by weight in water, followed by further application of
water. The mixture when initially sprayed onto a fire at
a flow rate of about 4.5 L/min to 7.5 L/min will generate
a thick layer of foam containing carbon dioxide. At these
flow rates, the pressure is about 30 psi to 100 psi. This
thick layer of foam smothers the burning flame rapidly,
within 2-10 seconds. _When followed by the application of
water, further foaming is generated together with rapid
cooling of the hot oil/grease. An application of water
for 2 minutes at a similar flow rate of about 4.5 L/min to
7.5 L/min causes more foaming and at the same time reduced
the temperature of the hot oil to below 330 C. so that re-
ignition is prevented.
Apparently, the unique mixture when applied to
the burning oil absorbs a large amount heat from the oil.
It has been found that at a flow rate of about 4.5
L/min/nozzle - 7.5 L/min/nozzle, a 2-10 sec. application
of a 25 wtt solution of a mixture of potassium bicarbonate
with sodium sulfate in a molet ratio of 85:15 followed by
a 2-10 minute application at the same flow rate of water
completely extinguishes an actively burning deep fryer
containing about 50 L. (13 gal.) of cooking oil.
Furthermore, the oil is cooled down to below 330 C to
prevent re-flash.
The present system provides various operating
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options. The extinguishing agent can be any known
extinguishant or is preferably the salt mixture disclosed
in the copending application discussed hereinabove. The
extinguishant can be employed as a liquid solution or the
system can be designed to employ an extinguishant in dry
solid form which is converted to a liquid solution when
the system is activated.
There are also various extinguishing agent
storage options. The extinguishing agent can be contained
in one or more containers under compressed gas pressure in
a dry pipe system. In another embodiment, the
extinguishant can be contained in one or more containers
under atmospheric pressure in a dry pipe system. In still
another embodiment liquid extinguishant can be contained
in the discharge piping under compressed gas pressure as a
wet pipe system.
There are also various water valve actuation
options including:
a) gas pressure;
b) water pressure;
c) spring-loaded trip mechanism;
d) electric solenoid; and
e) a combination of above
Agent expellant options include:
a) gas pressure;
b) water pressure;
c) gas/water pressure combination; and
d) an eductor suction.
Compressed gas storage options include:
a) gas cartridge or
b) agent tank (stored pressure).
